Treatment of refractory auriferous ores.



UNITED fiTATlES PATENT @llllhlltllfi JOHN HENRY NIEMANN, 0F ADELAIDE,SOUTH AUSTRALIA, AUSTRALIA.

TREATMENT OF REFRACTORY AURIFEROUS ORES.

No Drawing.

To all whom it may concern:

Be it known that 1, Joan HENRY NIE- MANN, a subject of the King of GreatBritain, residing at 20 Waymouth street, Adelaide, in the State of SouthAustralia, in the Commonwealth of Australia, chemist, have inventedcertain new and useful Improvements in and Relating to the Treatment ofRefractory Auriferous Ores, of which the following is a specification.

This invention relates to an improved method of economically extracting,separating, and recovering the precious metal constituents of refractoryauriferous ore or orestufi containing selenium, or seleniferous materialyielding a salt or compound of selenium.

From experiments, I have found that solenium in the presence of certainelements or compounds possesses some especial decomposing or doubledecomposing properties; for instance it combines more readily with thereduced metal than the liberated oxygen; it has a special selectiveaifinity .or metals most frequently found free or natively pure, such asgold, bismuth, and copper; and it combines most readily with metalswhich most readily part with their oxygen such as mercury, silver, iron,lead, and arsenic.

As selenium and gold have a selective afinity for each other, forminggold selenid, and selenid of gold may be readily converted into solubleseleno-cyanid of gold, also selectively, I have found that the greaterpart of the gold in auriferous ore either natively or artificiallycontaining or yielding selenium, may be dissolved in a cyanid solution,quickly, and cheaply, and selectively, and recovered by the utilizationof the selenium in a cyaniding operation followed by retorting in themanner hereinafter described.

I therefore accomplish my objects of effectually dissolving, separatingand recovering the gold, and of separating and recovering the otherdesirable constituents from refractory auriferous ore, either nativelyor artificially containing or yielding selenium, after the additionthereto where necessary of seleniferous ore, or material yielding a saltor compound of selenium, by controlling and utilizing the decomposing ordouble decomposing effect of selenium, upon the metallic constituents ofthe auriferous material; and, by checking the oxidation of Specificationof Letters Patent.

Application filed July 14, 1913.

Patented Apr. 11?, 191?, Serial No. 779,015.

the sulfids, selenids and arsenids of the base metallic constituents,from the initial crushing of the material to the final smelting of theresulting bullion; and, by utilizing and controlling other inherentpeculiar properties of selenium such as its special afiinity for certainmetals, and its peculiar solvent, thermal, electrical and chemicalaction in the dissolving deposition, separation and refining of gold, bysubjecting the crude ore with the contained or admixed selenium to agrinding or crushing operation with or in a weak solution of cyanid, toform a soluble seleno-cyanid of gold, during which process the oxidationor oxygenation of the material or the solution is prevented as much aspossible in order to minimize the formation of seleno-cyanids of basemetals. The re sulting cyanid solution is passed through zinc boxes toextract the gold from solution; and the resulting depositions orprecipitates are retorted without the admission of air, wherein thesublimable elements or compounds are sublimed and collected and treatedas hereinafter described; and the auriferous residue left in the retortis smelted.

F or the purpose of my invention, I crush and grind the crude auriferousore or metalliferous material by usual methods, except that instead ofwater and in order to prevent oxidation I use at the outset a weakcyanid solution of a suitable strength, adjusted according to assayresults as with ordinary cyanidation. With the same cyanid solution, thefinely ground material is then transferred to and agitated within vats,preferably deep and covered, for say twentyfour hours or until therecoverable gold is dissolved under ordinary working conditions.

The cyanid solution used for crushing and grinding purposes, is pumpedback repeatedly and re-used. This insures the dissolving of the bulk ofsuch gold as may at first float on the surface, in the form of selenid,filmy or float amalgam, or in other combinations or forms, while theagitation process in sures the solution of the remainder of such gold,thus preventing all flotation loss.

The use of cyanid solution at the outset, in the presence of selenium,shortens the time required for dissolving the gold, while the re-use ofthe cyanid solution has the ad ditional advantage of enabling the ore tobe crushed and treated with great economy of Water.

7 the mass,

After treatment in the agitator vats, and clarification in settlingvats, the cyanid solution containing the dissolved gold is run throughextractor boxes of ordinary type, and electrolyzed if necessary, toassist the deposition or aggregation of precipitates, or such as theevolution of hydrogen accompanied by the solution of zinc fines from thezinc boxes.

During the process of extraction and deposition of the gold fromsolution, the moderate and regular evolution of hydrogen normally occursand is insured by usual methods, in order to promote the evolution ofarseniureted or antimoniureted hydrogen should arsenic or antimony bedeposited in the extractor boxes.

Immunity from volatilization loss, through the formation of seleniuretedor sulfureted hydrogen, is insured, because these gases form selenids orsulfids of metals held dissolved in the cyanid solution, and are precipitated in the boxes as selenids or sulfids; a further precautionagainst loss being taken, by passing the solution issuing from theextractor boxes through a suitable filtering apparatus interposedbetween the box and the sump, whereby I arrest any gold which mightotherwise escape as a flocculent selenid.

All the metalliferous constituents deposited upon the plates, orprecipitated therefrom as slimes, are collected, well washed with water,and drained well. If necessary they are then mixed with such materialsas may be required to prevent the caking of to regulate decomposition orto specially promote the sublimation of volatile metallic constituentssuch as mercury.

The drained slimes alone, or the drained slimes mixed with othermaterial as before described, are then heated for eight (8) hours, moreor less, in a suitable retort and allowed to cool.. The retort isconnected with condensing chambers to arrest the sublimates, which maycontain some gold and silver, mixed with the selenium, zinc, arsenic,lead, sulfur, and other volatile elements, the elimination of which, isthe object of the retorting process. Owing to the double decomposingaction of selenium, these volatile elements are as efiectually liberatedfrom their combinations in the retort, without access of air, as withthe ordinary roasting or other open air processes. These sublimates arecollected, and retorted again, preferably by fractional methods, whichis essen- Gopies of this patent may be obtained for tial if bismuth be aconstituent of the material treated. The bullion left in the retort, asa fine powder, is smelted by ordinary methods, except that if anyselenium be retained by the bullion, the crucibles used, and the fluxesemployed, are necessarily those best adapted for conducting the smeltingoperation in an atmosphere free from oxygen. 7

If necessary to further prevent oxidation, hydrogen or other suitablegases may be passed into the molten metal in the crucibles. Should thebullion after this treatment, still contain selenium, it may be alloyedwith copper and electrolyzed to separate the selenium by the methodsusually employed for the recovery of gold from copper electrolytically,before being re-smelted.

I claim,

1. The method of treating refractory auriferous ore, which comprisescomminuting the unroasted ore in the presence of selenium or a seleniumcompound and a weak cyanid solution while excluding air or oxygen.

2. The method of treating refractory auriferous sulfid ores, whichcomprises forming a solution containing selenocyanid of gold from thenative ore, maintaining said 'solu tion substantially free fromoxidation, and causing the precipitation of the gold from said solutionunder substantially non-oxidizing conditions with relation to selenium.

3. The method of treating refractory auriferous ores, which comprisestreating the raw ore with a weak cyanid solution in the presence ofseleniferous material under nonoxidizing conditions, causing theprecipitation of gold from said solution under like conditions inslimes, and retorting the slimes in a non-oxidizing atmosphere.

4. The method of treating refractory auriferous ores, which comprisestreating the raw ore with a weak cyanid solution in the presence ofseleniferous material and under non-oxidizing conditions, precipitatingthe gold from the solution in slimes in a nonoxidizing atmosphere,distilling the slimes to recover values other than gold, and retortingthe gold residues in a reducing atmosphere.

In testimony whereof I have afiixed .my signature in presence of twowitnesses.

' JOHN HENRY NIEMANN. Witnesses: CHARLES HARKELL, LUCY GREEN.

five cents each, by addressing the (Commissioner of Patents,

Washington, D. O.

